1. Field of the Invention
This invention relates broadly to surgical devices. More particularly, this invention relates to orthopedic implants, and specifically to elements to implant and shape a bone plate.
2. State of the Art
Fracture to the metaphysis of a long bone can be difficult to treat. Improper treatment can result in deformity and long-term discomfort.
By way of example, a Colles' fracture is a fracture resulting from compressive forces being placed on the distal radius, and which causes backward or dorsal displacement of the distal fragment and radial deviation of the hand at the wrist. Often, a Colles' fracture will result in multiple bone fragments which are movable and out of alignment relative to each other. If not properly treated, such fractures may result in permanent wrist deformity and limited articulation of the wrist. It is therefore important to align the fracture and fixate the bones relative to each other so that proper healing may occur.
Alignment and fixation of a metaphyseal fracture are typically performed by one of several methods: casting, external fixation, pinning, and plating. Casting is non-invasive, but may not be able to maintain alignment of the fracture where many bone fragments exist. Therefore, as an alternative, external fixators may be used. External fixators utilize a method known as ligamentotaxis, which provides distraction forces across the joint and permits the fracture to be aligned based upon the tension placed on the surrounding ligaments. However, while external fixators can maintain the position of the wrist bones, it may nevertheless be difficult in certain fractures to first provide the bones in proper alignment. In addition, external fixators are often not suitable for fractures resulting in multiple bone fragments. Pinning with K-wires (Kirschner wires) is an invasive procedure whereby pins are positioned into the various fragments. This is a difficult and time consuming procedure that provides limited fixation if the bone is comminuted or osteoporotic.
Plating utilizes a stabilizing metal plate typically placed against the bone, fixed-angle fasteners (which may have threaded or non-threaded shafts) positioned through the plate and entering drilled holes adjacent an articular bone surface, and cortical screws extending from the plate into holes drilled in the bone to provide stabilized fracture fixation. For example, co-owned U.S. Pub. No. 20040193164 A1, which is hereby incorporated by reference herein in its entirety, discloses a plate particularly adapted to treat dorsally displaced metaphyseal fractures from the volar side of the wrist.
When fixed-angle fasteners are utilized in conjunction with a bone plate, it is necessary to ensure that the pilot holes drilled for the fasteners are co-axial with the hole axes. Otherwise, the shaft of the fasteners will not properly align with the anatomy, and the head of the fasteners will not properly align with the threaded holes of the plate, potentially resulting in cross-threading. As a result, with the plate placed upon the bone, prior to drilling each hole in the bone in alignment with a threaded hole, a drill guide is attached to the plate at the threaded hole. The guide defines a tubular passage which directs the drill bit in the proper orientation for a fastener through the particular threaded hole. After drilling each hole, the drill guide is removed, the fastener is inserted in the threaded hole, and the drill guide is coupled to a subsequent threaded hole.
The process of attaching the drill guide during the surgical procedure is laborious. It can be difficult to locate the appropriate angle for threadably coupling the guide to the peg hole during the procedure, given that each threaded hole may have a discrete axis angle from the other threaded holes. Such difficulty can unnecessarily prolong the surgical procedure.
Furthermore, fragment plates are commonly used to fixate fractures along the diaphysis of a bone or at specific diaphyseal-metaphyseal or metaphyseal locations. Such plates are generally elongate, L-shaped, Y-shaped or have another shape which is suited for placement on a portion of a bone. The plates can be of varying length depending upon the intended fixation application. When fragment plates are provided with threaded holes they are subject to the same practical labor intensity for use as presented above with respect to the volar plate; i.e., it is laborious to attach a drill guide at each threaded hole for drilling a hole in alignment with the axis of the hole for receiving the fixed angle fastener therethrough.
In addition, the anatomy for which the fragment plates are designed often differ from the exact contour of the bone contacting surface of the plates. For several reasons it has been impractical to re-contour a fragment plate with threaded holes during the implantation procedure to better fit the anatomy. First, in distinction from non-fixed angle fragment plates, inserting shaping tools into the threaded holes of the plate and applying a force to the plate with the tools will distort the threads making such holes unaccepting to their threaded fasteners. Second, to best fit the anatomy a plate may need to be re-contoured in three dimensions: longitudinal, lateral, and twist. Such modifications are difficult to transfer to a very stiff metal plate, having to place the plate on the bone, remove the bone reshaping, placing the plate back on the bone, making corrections, etc. That is, it is very difficult to reshape any plate to closely fit the bone when such reshaping is done at a distance from the bone.